Pulse signaling system



Nov. 3o, 194s.

.Filed April 17, 1945 E. LABIN ETAL.

PULSE SIGNALING SYSTEM 2 Shets-Sheet 1 E; LABIN ETAL PULSE SIGNALING SYSTEMv Nov'. 30,

2 Sheets-Sheet 2 Filed April 17, 1945 A L 0 A 5 NL l wm EAM .me MMM. Ow HMP M PULSA-'S W/TH REDUCED DUPL/ICEME/YT 75M. PULSES a BL 05W/N6 WA VE 5 G R L m mW@ 0 mwa T VLD. T mf /A am mm .system utilizing both of Patented Nov. 30, 1948 UNITED STATS PULSE SIGNALING SYSTEM Emile Labin,

Forest Hills, N. Y., assignors phone and Radio Corporation,

New York, and Donald D. Grieg,

to Federal Tele- New York, N. Y.,

a corporation of Delaware Application April 1'7, 1945, Serial No. 588,844

(Cl. Z50-20) 17 Claims.

p 1 This invention relates to pulse signal systems of the pulse time or phase displacement character. In transmitting systems employing pulse time .or phase displacement principles, a certain `amount of interference occurring during the time intervals between the pulses can be removed by blocking the interval occurring between the limits of modulation of the pulses. This form of.v interference elimination is particularly helpful where the maximum displacements of pulses are small compared to the time intervals between maximum limits of displacement of the pulses. Another useful method of increasing signal-tonoise ratio is to increase the maximum limits of time modulation in the transmitter. This effect, however, reduces the permissible blocking intervals in the receiver so that little net gain in signal-to-noise ratio is obtained.

It is an object of this invention to provide a the above mentioned methods of improving signal-to-noise ratio in pulse systems operating on the time displacement principle of modulation.

Another object is to provide a method and means for changing the time displacement of pulse time modulated signals either to reduce or to increase the time displacements of the pulses, as may be desired.

Another object of the invention is to provide a method and means for feeding back signal energy, either as a positive or negative feedback, in pulse time demodulator systems for changing substantially proportionately the time displacements of the time modulated pulses.

Another object is to provide a pulse time modulation receiver with means for changing, either to reduce or increase, the time displacement of the time modulated pulses and to block the intervals provided between the pulses, either before or after the time displacement changing operation.

A feature of the invention is to provide a feedback arrangement for either increasing or decreasing proportionately the time displacements of T. M. (time modulated) pulses. According to one method of the invention, the'signal energy is obtained by translating the time displacements into audi-o frequency energy and then applying the audio energy to a modulator circuit located in the input connection to the T. M. (time modulation) demodulator. Where it is desirable to reduce the degree of time displacement of the pulses, this may be accomplished by inverting the phase of the audio frequency energy so as to modulate the time modulated pulses in an opposite direction with respect to the initial modulation. The amount of feedback or change in time displacement may be determined by controlling the amplitude of the feedback energy. To in crease the time displacements -the feedback energy is applied in phase with the modulation so as to add further to the time displacements in the same direction as initially applied,

According to a furtherfeature of the invention, the interference occurring between the pulses, particularly between the limits of modulation thereof, may be blanked out by a suitable blocking wave produced in response to the average timing of the time modulated pulses. vThis blanking operation, however, may be performed by waves produced directly in response to each individual pulse as it is received, each resulting wave or undulation being used for blanking the interval following the pulse. The blanking -operation may also be located either prior to the time displacement changing circuit or at a point following it.

For a better understanding of the objects and features of the invention, reference may be had to the following detailed disclosure and the accompanying drawings in which:

Fig. 1 is a schematic diagram of a receiver circuit according tothe invention; l

Fig. 2 is a graphical illustration useful in explaining the operation of the invention; and

Fig, 3 is a schematic diagram of a modified form of the invention. l

Referring to Fig. 1, a radio carrier receiver and detector I is shown-for receiving by means of antenna 2, pulse modulated carrier energy from a transmitter 3 where the pulses aretime modulated with respect to a regular timing in response to intelligence signals. According to the present invention the time displacements at the transmitter 3 are large so as to provide an improved signal-to-noise ratio for `the signals for transmission.

In Fig. 2, graph A shows a sinusoidal signal wave 4 representative of the modulating energy `that may be employed at the transmitter 3.A The graph B represents a blocking wave 5 and a' train of time modulated pulses 6 to I4 received from transmitter 3 and detected at i, the pulses being modulated according to the wave energy '4. The detected pulses 6 to i4 are shown to be timedis placed between the limits of modulation l5,` l, the pulses B and i4 representing the maximum negative modulating signal potential and the pulse lll representing the time positions after modulation in response to the maximum positive signal potential. The other pulses represent time displacements varying between these two limits, the pulses 8 and I2, for example, representing zero modulation. The wave 5 represents a blocking potential that may be used for blanking out interference and other energy occurring during the time intervals between limits I5 and I6 of adjacent pulses.

The pulses 6 t0 I4 are applied over connection I1, Fig. 1, to a time displacement changing oircuit I8 which may be in the form of any one of a plurality of pulse time modulating circuits depending, of course, upon the particular type of pulse time modulation employed. The form shown for purposes of illustration is of the inductance delay type whereby the input pulses are delayed more or less depending upon the amplitude of the potential applied thereto over connection I9. This type of modulator circuit is disclosed in the copending application of Emile Labin, Serial No. 546,378, filed July 24, 1944, now Patent No. 2,445,783, which issued July 27,1948. The circuit includes an inductance coil 2c having an iron core 2|. The input connection I7 is applied thereto through a blocking condenser 22 and the ends of the coil are connected through condensers 23 and 24 to ground.

The output of the modulator circuit I8 is preferably applied to an amplifier 25 and then to a T. M. .demodulator 26 whereby the time displacements of the pulses are translated into amplitude displacements and applied to a low pass lter 2l yto remove the pulse component. This results in an audio signal wave which may be applied directly to earphones 28 or other utilization cir- 3;

cuits. The audio signal waveis also applied over connection 29 to a phase inverter Sli, amplitude control device 3|, the gain of which may be ad- .usted, and thence over connection I9 to the modulator I8.

In Fig. 2, graph C represents the audio signal wave l22 after the phase and amplitude thereof has been controlled as desired at 30 and 3i. It will be understood, of course, thatthe time relationship of the different graphs in Fig 2 may be varied in actual practice from that shown, but for purposes of illustration the relations shown may be regarded as indicating the operating principles of the invention. When the wave 32 is applied to the modulator I8, the pulses 6 to It applied thereto over connection I.'I are further displaced according to the potential of the wave 32, the amplitude of which is controlled at SI. This Yfurther modulation changes the time positions ofthe input pulses substantially as indicated at 6' to I4', graph D. Referring particularly to pulse 6, the time position of which corresponds to the maximum negative potential of the initiating modulating wave 4, the new position indicated at 6 is displaced an amount t1` equal to substantially one half the amount of the maximum displacement indicated by limits I5 and I5. The

pulse IU which corresponds to the maximum posi- `tive potential of the signal is theoretically undisturbedby the modulating operation of circuit I8. As va matter of fact, some modulation will occur dueto the displacement relation of pulse I0 with `respect to the maximum positive potential point on curve 32, but this is only a slight amount com- .pared to the modulation of pulse 6. The pulses 1, 8 and 9 between these two limits are shifted in time displacement by amounts te, t3 and t4 respectively corresponding to the amplitude and phase of the feedback energy 32.

For simplicity of illustration, any inherent de- 4 lay produced by the circuit IB for modulating energy corresponding to the negative maximum of signal wave 32 has been disregarded. Other types of modulating circuits having zero or some other modulating effect for the maximum negative potential value may be used in place of the particular modulator I8.

Graph E represents the signal pulses as they occur in the output of the circuit I8, the new limits of modulation being indicated at I5 and I6'. It will be clear that the intervals T1 occurring between the limits of modulation of adjacent input pulses, graph B, are considerably smaller than the intervals T2 occurring between the limits of modulation of the output pulses of circuit I8. By applying the signal pulses over connection 33 toa tuned circuit of a known wave producer 34, a suitable blocking wave having a frequency corresponding to the average repetition rate of the signal pulses may be obtained. By shaping and phasing the wave at 35, a substantially rectangular blocking wave 36 is produced as a control potential for amplifier 25, whereby interference or other energy occurring during the intervals btween the pulses is blanked out. It will be clear according to our invention that 4the reduction of the time displacement of the pulses at the receiver enables the blanking out of a much greater time interval than was possible prior to the displacement reducticn as is clear from a comparison of blocking waves 5 and 36.

In Fig. 3, a circuit has been shown similar to Fig. l except that the feedback energy is fed back in phase with respect to the phase of the initial modulating signalvenergy. The phaseinverter 30 therefore has been omitted in this embodiment. The other elements are the same as indicated by like reference characters except that the amplifier 25 is located in the input to modulator I8 as indcated at 25d. It will `be clear that the feedback of audio wave energy from filter 2l to the modulator i8 being in phase with the initial modulation of the time modulated pulses applied to the modulator i8 will act in the nature of a positive feedback energy and thereby increase further the time displacements of the time modulated pulses. In this connection, it might be added that increased time displacement is desirable for certain forms of demodulator circuits. In such a circuit, the blocking operation is preferably performed before the time displacement changing operation. rllhus, the amplifier 25a is controlled by the blocking wave from generator 34 to blank out any interference occurring in the intervals between input pulses.

Those skilled in the art will recognize that many changes and various modications of the invention may be made without departing from the principlesk thereof. For example, either pushpull time modulated pulses, a different form of modulator and possibly also a dilTerent form of demodulator may be employed, and it may be desirable even to use other circuits in conjunction with the modulating feedback operation. It

is to be understood, therefore, that the embodiments herein shown. and described are submitted by way of illustration of the invention only 'and not as a limitation of the scope of the invention as set forth in the objects and the appended claims.

We claim:

1. A method of changing the time displacement of time modulated pulses comprising demodulating the time modulated pulses to obtain the signal energy thereof, and time modulating 5 the time modulated pulses with the energy thus obtained.

2. A method of changing the time displacement of time modulated pulses comprising de modulating the time modulated pulses to obtain the signal energy thereof, time modulating the time modulated pulses with the energy thus obtained, and controlling the amplitude of the signal energy to determine the amount of change desired by the modulating operation.

3. A method of reducing the time displacement of time modulated pulses comprising demodulating the time modulated pulses to obtain the signal energy thereof, and time modulating the time modulated pulses in phase opposition with respect to the phase of the initial modulation of the pulses.

4. A method of increasing the time displacements oi time modulated pulses comprising demodulating the time modulated pulses to obtain the signal energy with which the pulses are modulated, and time modulating the time modulated pulses with the signal energy thus obtained in phase with the initial modulation of the pulses.

5. A method of improving the signal-to-noise ratio of time modulated pulses comprising reducing the time displacement of the pulses to increase the time interval between the maximum limits of time modulation of the pulses, and blocking the energy occurring during said time intervals.

6. A method of improving signal-to-noise ratio of time modulated pulses comprising reducing the time displacements of the pulses, and blocking the energy occurring during the time intervals resulting between the new .time modulation limits of the pulses.

7. A method of improving signal-to-noise ratio of time modulated pulses comprising increasing the time displacements of the pulses, and blocking the intervals between the time modulation limits of the pulses prior to the displacement increasing operation.

8. A method of improving signal-to-noise ratio of time modulated pulses comprising reducing the time displacements of the pulses, translating the time modulation of said pulses into amplitude modulated energy, applying said energy in phase'opposition to the modulation of said pulses as a further modulating energy to reduce the time displacements of said pulses, and blocking the energy occurring during the time intervals resulting between the new time modulation limits of the pulses.

9. Means for changing the time displacement of time modulated pulses comprising means for translating the time modulated pulses into amplitude modulated energy, and means to modulate in time the time modulated pulses according to the amplitude modulated energy thus obtained.

10. A means according to claim 9 wherein the means for translating the time modulated pulses include means for controlling the amplitude of the amplitude modulated energy.

11. A means according to claim 9 wherein the means for translating the time modulated pulses include means for controlling the phase of said energy to determine the direction of the change in time displacement.

12. A means according to claim 9 wherein the means for translating the time modulated pulses include means for controlling the phase and amplitude of said energy to determine the degree and direction of the change in the time displacement.

13. Means for changing the time displacement of time modulated pulses comprising a time mod-- ulator, means to apply time modulated pulses to said modulator, a demodulator for translating the pulse output of said modulator into amplitude modulated energy, and means to apply the output energy of said demodulator to said modulator to vary the time displacement of the pulses.

14. Means for changing the time displacement of time modulated pulses comprising a time mod-- ulator, means to apply time modulated pulses to said modulator, a demodulator for translating the pulse output of said modulator into amplitude modulated energy, means to control the phase of said energy, and means to apply the output energy to said modulator to vary the time displacement of the pulses applied thereto according to the amplitude and phase relation of said energy.

15. Means for improving the signal-to-noise ratio of time modulated pulses comprising means for translating input time modulated pulses into amplitude modulated energy, means responsive to said energy to reduce the time displacement of said pulses, a blocking circuit, and means to derive a blocking wave from the average timing of said pulses for application to said blocking circuit to blank out energy occurring during the major part of the intervals between the pulses following the displacement reduction thereof.

16. In a receiver for time modulated pulses, a time displacement changing circuit, means to apply the input time modulated pulses to said circuit, a demodulator for translating the time modulated displacements of said pulses into amplitude varying energy, means for inverting the phase of said output energy, means to control amplification of said energy, means to apply the output energy thus controlled as to phase and amplitude to said displacement changing circuit to modify the time displacements of said input pulses, means controlled by said input pulses to produce a blocking wave and means employing said blocking wave to block energy occurring during the time intervals between time modulated pulses enlarged by said displacement changing circuit.

17. In a receiver for time modulated pulses, a time displacement changing circuit, means to apply the input time modulated pulses to said circuit, an amplifier to receive the output of said circuit, a demodulator for translating the time modulated displacements of said pulses into amplitude varying energy, means for inverting the phase of said output energy, means to apply the output energy thus controlled as to phase to said displacement changing circuit to modify the time displacements of said input pulses, means controlled by said input pulses to produce a blocking Wave, and means to apply said blocking wave to said amplifier to block the intervals between time modulated pulses.

EMILE LABIN. DONALD D. GRIEG.

No references cited. 

